The present invention relates to bitmap image processing technology, and more particularly, to systems and methods thereof for image correction.
A bitmap image is a map or organized array of pixels of bit-based information, often mapped at hundreds of pixels. For example, an 3 inches by 2 inches bitmap image with a resolution of 300 pixels per inch produces 900 pixels by 600 pixels-, that is, 540000 pixels totally.
The bitmap image contains three types of images, black and white, grayscale, and RGB. A black and white bitmap image contains the least information for each pixel, i.e., information regarding whether each pixel is black or white. Using the binary counting method, a grayscale bitmap (black to white) has a color depth of 256. Each pixel is represented as having one of 256 different grays (values), including black and white. An RGB bitmap image has a color depth of 16.77 million colors, 256×256×256. Each pixel has information for each of the 3 RGB colors. Each pixel in the bitmap array describes a layer of one of 256 values for red, one of 256 values for green and one of 256 values for blue.
Scanning documents by reflective scanners have been used in a variety of processes for digitalizing an original document to a machine-readable version (i.e., a bitmap image). A problem associated with digitizing an original document is bleed-through, wherein a pattern interferes with text and/or images to be digitalized due to the penetration from the reverse side of scanned monochromic or chromatic documents, resulting in digitalization degradation. FIG. 1 is a schematic diagram of a conventional digitalized bitmap image. Area 11 is a bleed-through pattern penetrating from the reverse side of a scanned document after scanning. In addition to bleed-through patterns, watermarks may also degrade the digitalization, and both bleed-through patterns and watermarks can be defined as shadow patterns. In view of these drawbacks, a need exists for a system and method of image correction that removes shadow patterns from bitmap images.